micobes.jpg
Figure 1[1] : An example of a microbe.

Biodegradable polymers are designed to degrade upon disposal by the enzymatic action of microorganism such as bacteria, fungi, and algae.[2] Biodegradation occurs through the action of enzymes in microorganisms in soil, sewage and compost areas, these areas are highly complex biological environment with hundreds of different types of microorganisms. Different microorganisms display different biodegradation abilities.[3] Enzymes can can attack the polymer in two ways. The first way is random attack anywhere on the polymer chain, known as endoenzyme mechanism. This type of attack results in a broken down polymer chains of various molecular weights. The second way is attack by microorganisms on only the terminal units, this results in removal of terminal units as monomers, dimers and trimers, this is known as exoenzyme attack (see Figure 2).

degradation_of_polymers.gif

Figure 2[3]: A visual representation of the action of exoenzyme and endoenzymes. Exoenzymes attack terminal ends and break off a monomer or a chain of small number of monomers. Endoenzymes attack randomly on the polymer chain and break the a long chain into small polymer chains.

Biodegradation is an immensely complex process because of the relationship between the chemical, physical and property of the polymer and the different types of environment in which the degradation is taking place. The complexity of the process means it is not possible to easily specify the unique steps that constitute the degradation process. Below are simple descriptions of some of the variety of ways in which polymers can be biodegraded by microorganisms.[3]

This section will talk about:

Biodegradability of Cellulose polymers

Biodegradability of Starch Polymers

Biodegradability of Polyester Polymers

Biodegradability of Polyethylene and Hydrocarbon Chains



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  1. ^ Dicover Magazine. 2010 March. I for one welcome our microbial overloads [Internet]. Carl Ziemmer. [Cited 2012 April 8]. Available from:
    http://blogs.discovermagazine.com/loom/2010/03/04/i-for-one-welcome-our-microbial-overlords/
  2. ^ Gross RA, Kalra B. 2002. Biodegradable polymers for the environment. Science. 297: 803-807.
  3. ^ Lenz RW. 1993. Biodegradable polymers. Advances in Polymer Sciences.107:1-40.